Variable capacity compressor



April 1944- A. B. NEWTON VARIABLE CAPACITY COMPRESSOR Filed Nov. 9, 1940 INVENTOR. Alwim B.Nzw1'on ATTORNEY Patented Apr. 18, 1944 UNITED stares i @FFECE VARIABLE CAPACITY COMPRESSOR Alwin B. Newton, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator (Jompany, Minneapolis, Minn, a corporation of Delaware Application November 9, 1940, Serial No. 365,097

Claims.

by obtain a variable unloading for the compressor. I

Another object is to provide a variable linkage for a valve operator to cause a compressor to operate difierently for difierent values of a variable condition, such as temperature, humidity, pressure, or a combination of these conditions.

A further object is to provide a variable capacity compressor in combination with a constant speed motor and a refrigerating system in a manner to cause the compressor to change in capacity to thereby vary the cooling effect of the system.

Another object is to provide a variable capacity compressor wherein theefiiciency is maintained within predetermined limits and loading of the driving motor therefore is kept at or below a suitable maximum value.

Other objects reside in the novel structure of the compressor and will be in part obvious and in part .pointed out in the accompanying specification and in the claims.

In the drawing:

orator H. The compressor ill is controlled by a condition responsive device 2| which may take the form of a temperature device, humidity device, or a pressure responsive device, any of which ar conventional and well lmown in the art.

The compressor I0 comprises a suitably cooled cylinder 25 within which a piston 2fi -reciprocates. The piston 26 is driven by a crank 21 which is shown as formed integrally with a shaft 28 suitably journalled in the hubs 29 and 30. Th shaft 28 is secured to the driven wheel l2 so that upon Figure 1 shows a detail sectional'view of a com- The compressor I0 is part of a refrigerating system comprising a condenser l5 which is connected to the head of the compressor l0 by a pipe i6, and an evaporator I! which is connected to the suction side of the compressor Ill by pipe I8. The condenser l5 and the evaporator H are connected together by the pipe l9. An expanrotation of the wheel the shaft will alsobe rotated.

A connection for the low pressure refrigerant pipe I8 is shown at 35. This connection communicates with the low pressure chamber within the piston which is defined between piston rings 32 and 33. An inlet valve 34 is arranged to cooperate with the upper part of the piston 2d. The valve 34 is normally biased to closed position by a spring 35 which urges the valve 34 downwardly into engagement with a valve seat. 35 in the top of the piston 26. A high pressure valve 40 is normally biased into engagement with a valve seat 4| at the top of the cylinder 26 by a spring 42.

The above described mechanism comprises the essential elements of a conventional refrigeration compressor. The device in the position shown, with the piston 26 in its uppermost position is exhausting refrigerant which has been compressed. The high pressure of the gas has forced the outlet valve 40 to leave its seat 4| to permit the compressed gas to escape into the head or the compressor. The piston 26 is shown as ready'to begin its downward stroke. Upon going downward the outlet valve 40 will be closed and the inlet valve 39 in the head of the piston 26 will be opened because there will be a partial vacuum created above the piston 26. At this time, gaseous refrigerant returning through th pipe l8 from the evaporator I! will pass through themlet valve 34 to the now expanding chamber defined between the inlet valve 34 and the outlet valve 40. When'the piston 26 reaches the lowermost point in its strok and reverses in direction of movement the flow of low pressure refrigerant will be out 01f because the inlet valve 34 will close. Upon the upward stroke of the piston 26, the low sion valve 20, which may take the form of a conventional constant pressure valve,'an evaporator temperature operated valve, or a superheat valve, isin control of the refrigerant as it flows through pressure gas which has been sucked in between the inlet and outlet valves will be compressed. When the gas is compressed to a sumcient degree to insure proper condensation thereof, the outlet valve 40 will be raised from the seat by this pressure. This pressure is determined by the spring the pipe I 9 from the condenser I5 to the evap- 42 which biases the outlet valve 40 downwardly.

cal slot is provided so that the shoe may re- 53 to shorten this linkage.

The above described action is the operation for one complete cycle in the conventional refrigerant compressor. In other words, the operation of the inlet and the outlet valves is determined solely by the pressure of the refrigerant and the direction of o eration of the piston 25.

Means to modify the operation of the compressor comprise links 45 which are suitably pivoted at 45 to the compressor head case and also pivoted at 41 to the valve 45. The links 45 have slots 48 within which a pin 49 is free to slide horizontally but not vertically. This slot is at the opposite end of the links 45 from that end which is pivoted at 45. It is therefore seen that a lever is formed by these links which is adapted to actuate the valve 45. The actuating pin 45 is suitably secured to a vertically reciprocating rod 55. The bottom of the rod 55 abuts a shoe on the bottom of which is a cam surface 52. A cam surface 53 is formed on a shoe 54 which is driven by a vertically reciprocating rod 55 that has a cam follower 55 on the bottom thereof that follows a cam 51 suitably fixed for rotation upon the driven shaft 28. The rod 55 is biased downwardly by a spring 58 to thereby hold the cam follower-55 into firm engagement with the cam 51. It is therefore seen that a linkage is provided which may also operate the outlet valve 45. When the cam 51 driven by the shaft 28 has its high surface upward, as shown in Figure 1, the shaft 55, the shoe 54, the engaging cam surfaces 52 and 53, the shoe 5|, and the rod 55, wfll all be raised to thereby raise the pin 45. When the pin 45 is raised the links 45 will also be raised and rotate about the fixed pivot 46 to hold the valve 45 away from its seat 4|.

In this manner the valve 45 as well as being operated by the pressure of the refrigerant is additionally operated in accordance with the position of the cam surfaces 52 and 53 of the shoes 5| and 54, respectively. w Means to adjust the positions of cam surfaces 52.and 53 are'generally indicated by the reference character 55. The means 55 may take the form of a modulating motor, as shown, or some pressure responsive device such as a bellows or a diaphragm if desired. Whatever form of condition responsive means used, each must be capable of' reciprocating a shaft 5|. This shaft 5| extends through a mounting plate 52 and is sealed by means of a sealing bellows 53 to form a gas tight seal at the entrance point of the rod 5|. The rod 5| may then fit rather loosely through a hole 54 which is provided in the plate 52 so that the rod 5| may be rocked enough to allow for the eccentricity of the driving cam 55 which positions the rod 5|. The rod 5| is provided on its inner end with a pin 55 which fits into a vertical slot 51 in the shoe 5|. This vertiupwardly on the cam surface 53 to thereby. 6

lengthen the effective linkage between the cam follower 55 and the pin 49 which operates the valve actuating links 45. Conversely when the shoe 5| is moved toward the left the cam surface 52 will be moved downwardly on the cam surface When the linkage is shortened the portion of the cycle of rotation of the shaft 28 which will hold the outlet valve 45 of the compressor open will be shortened, or it may be shortened to such an extent that 1 the valve will not be held open by this linkage for any portion of this cycle. As the linkage 1S graduatingly lengthened the valve will be held open a proportionately longer part of the cycle to thereby vary the operation of the outlet valve.

The linkage changing means 55 is under control of the condition responsive means 2|. As was previously pointed out the condition responsive means may take the form of temperature, humidity, or pressure controls. For example, if a temperature control, the device may be responsive to the evaporator temperature or to the temperature in the space conditioned to control the cooling. If humidity control is desired, a-

humidity responsive element may be placed in the space conditioned or in proximity to the evaporator coil and be responsive to the humidity in the medium controlled. If pressure control is desired, the device 2| could be suitably connected to some point in the refrigerating system, the pressure of which it is desired to control.

Operation The operation of a conventional compressor has been hereinbefore discussed. The operation of the compressor including the novel structure comprising the instant invention will now be described. It will be noted that the cam surfaces 52 and 53 are in engagement at approximately a mid point position of control of the compressor modifying means 55. In this position the compressor will be unloaded by approximately 50 per cent of its capacity. It will be notedthat the compressor piston 25 is just beginning its downward or suction stroke. It will also be noted that the valve adjustment linkage determined by the position of the cam surfaces 52 and 53 is holding the outlet valve 45 slightly away from the valve seat 4|. With the parts in the position shown, when the piston 25 begins its downward stroke some of the high pressure refrigerant will fiow past the outlet valve back into the cylinder 25. Thus the inlet valve 34 will not be opened as soon as it would be if the outlet valve 45 were closed and therefore will not admit as much low pressure refrigerant. The valve adjustment linkage will hold the valve 45 away from its seat until the cam 51 which actuates the linkage has turned through a portion of the cycle predetermined bythe position of the cams 52 and 53. When the piston 25 starts its upward stroke the low pressure gas then contained between the inlet and outlet valves will be compressed. After a pressure sufficient to cause the outlet valve 45 to leave the seat has been reached, this valve will be lifted therefrom to permit the now high pressure gas to pass out of the cylinder 25. However, the valve will be held away from the seat in the manner above described so that some of the high pressure refrigerant will return to the cylinder.

Assume now that the refrigeration load increases, that is, the demand by the condition controller 2| causes the compressor controller 55 to be adjusted in a manner to increase the compressor capacity. An increase in capacity is accomplished by moving the cam surface 52 to the left with respect to the cam surface 53, thus shortening the linkage connecting the cam to the valve actuating lever 45. With this'connecting linkage shortened, the outlet valve 05" will not be held away from its valve seat for as a; long a time as it would bein the mid point posi; tion previously discussed. If. the system load ,de;., ,3; creases the reverse of the above described action would obtain and the valve actuating linkage will be lengthened by moving the cam surface 52 to the right with respect to the cam surface 53. With this linkage lengthened the outlet valve 40 will be maintained in a position away from valve seat It for a longer portion of the cycle to thereby unload the compressor.

It will be noted in each of the conditions described in connection with the operation of the compressor that the piston in compressing the gas at all times works against the pressure neces-- sary to lift the outlet valve 40 away from its seat ag-ainstthe tension of the spring 42. Because of this, it is possible to select a motor for driving the compressor which may work up to its capacity load, or at a capacity under its highest load, but will at no time be caused to operate at a capacity greater than that of which it is capable. In this manner, a motor may be selected which will produce all of the work that it may without the danger of overloading the same and thus causing it to burn out.

While I have described one form that my invention may take, it will be clearly understood that many modifications thereof will occur to those skilled in the art. Many difierent forms, sizes and lengths of linkages for changing the 3. In a compressor, in combination, a cylinder, a piston reciprocable in said cylinder, said inder and said piston cooperating to form a compression chamber, a crank shaft operatively connected to said piston, inlet and outlet valves in communication with said compression chamber, said outlet valve opening outwardly from said compression chamber and being biased toward closed position, reciprocating means driven by operation of an outlet valve for a compressor will be devised. For example, means to vary the position of the cam driven by the compressor drive shaft might well be utilized, or some suitable toggle structure in the connecting linkage. Therefore, it should be understood that I am not to be limited in my invention only to those forms shown and described but by the scope ,of the appended claims and the prior art.

I claim as my invention:

1. In a compressor including a reciprocating piston operating within a piston chamber to deliver a compressed fluid, the combination of, an outlet valve for emitting compressed fluid from the compressor chamber, driving means for reciprocating the piston, a driven cam operated by said driving means, a reciprocable cam follower biased into engagement with said cam, a

first cam surface carried by said cam follower,-

a second cam surface in cooperative relationship to said first cam surface, a rockable link for operating said outlet valve, a connecting link between said rockable link and said second cam surface, said cam follower, said connecting link, and said rockable link being cooperatively arranged with said cam surfaces so that said driven cam may operate saidoutlet valve, and means for varying the relative position of said cam surfaces to thereby vary the action of said outlet valve.

2. In a compressor comprising a reciprocable piston and inlet and outlet valves for the compressing chamber thereof, the combination of, a

rockable link fixedly pivoted at one end and pivoted at another point to said outlet valve, a first reciprocablerod connected to the second end of said link, a second reciprocable rod, eccentric means operated simultaneously with said piston, biasing means for urging said second rod into engagement with said eccentric means, a first cam shoe connected to one of said rods, a second cam shoe connected to the other of said rods, said shoes abutting each other and being movable with respect to each other to vary the efiective length of the rods with respect to said eccentric means and said rockable link, and control means for relatively moving said cam shoes to vary the operation of said outlet valve.

said crank shaft and adapted to hold said exhaust valve open, after said piston starts on its intake stroke, and capacity regulating means for varying the portion of the intake stroke of said piston during which said exhaust valve is held open comprising means-for varying the efie'ctive length of said reciprocating means.

4. In a compressor, in combination, a cylinder,

.a piston reciprocable in said cylinder, said cyl inder and said piston cooperating to form a compression chamber, a crank shaft operatively connected to said piston, inlet and outlet valves in communication with said compression chamber, said outlet valve opening outwardly from said compression chamber and being biased toward closed position,.means for holding said exhaust valve open during portions of the intake stroke of said piston, and means for varying the proportion of the intake stroke of said piston dur ing which said exhaust valye is held open by said holding means.

5. In a compressor, movable means within a chamber for compressing a fluid, inlet means for said chamber, outlet valve means for said chamber, means biasing said outlet valve means toward closed position, driving means cyclically operating said movable means, the fluid pressure developed by operation of said movable means opening said outlet valve means against its bias during each cycle of said movable means, and means driven by said driving'means adiustably retarding the closing of said outlet valve means to permit a reverse flow of fluid through said outlet valve to vary the pumping capacity of said compressor.

6. In a. variable capacity compressor, movable means within a chamber for compressing a fluid, inlet valve means for said chamber, outlet valve means for said chamber, means biasing said valve means toward closed position, driving means operating said movable means in cycles wherein fluid enters said chamber through said inlet valve means in one portion of a cycle and the fluid compressed within the chamber leaves said chamber through the outlet valve means in means within a chamber for compressing a fluid,

inlet valve means for said chamber, outlet valve means for said chamber, driving means operating said movable means in cycles wherein fluid enters said chamber through valve means in one portion of a cycle of said movable means and leaves said chamber through valve means in another portion of said cycle, and capacity control means comprising adjustable means retarding the operation of one of said valve means so that its operation overlaps the operation of the other of said valve means to diminish the capacity of said compressor.

8. In a compressor, a piston for varying the sire of an expansible and contractible chamber to compress a fluid, a driven shaft for reciprocatin; said piston, an inlet valve for admitting low pressure fluid into said chamber to be compressed therein, an outlet valve for emitting compressed fluid from said chamber, and capacity control means comprising adjustable stop means controlling the closing of said outlet valve, said adjustable stop means comprising reciprocating means driven by said shaft, said reciprocating means including a connecting portion of adjustable length, the closing of the outlet valve during each stroke cycle of operation being controllably retarded by said adjustable stop means, the retarded closing of said outlet valve permitting compressed fluid to, enter said chamber through said outlet valve during the suction strokes of the compressor, whereby the pumping capacity 01 the compressor is reduced.

9. In a compressor, a piston for varying the size of an expansible and contractible chamber to compress a fluid, a driven shaft for reciprocating said piston, an inlet valve for admitting low pressure fluid into said chamber to be compressed therein, an outlet valve for emitting compressed fluid from said chamber, and means retarding the closing of said outlet valve, said means including reciprocating means driven by said shaft, said reciprocating means being adjustable in length while said compressor is in operation, the retarded closing of said outlet valve permitting compressed fluid to enter saidchamber through said outlet valve, whereby the pumping 10 capacity of the compressor is reduced.

10. In a compressor, an outlet valve therefor, means to actuate said outlet valve, outlet valve control means comprising cycling means operated simultaneously .with said compressor, said control 5 means operating to keep the outlet valve off its seat for a limited portion of each suction stroke of the compressor, and adjustable connecting means for said outlet valve control means for varying the length of said limited stroke portion during which said outlet ,valve remains ofi its seat during each suction stroke, whereby the pumping capacity of said compressor may be varied.

ALWIN B. NEWTON. 

